Differential gears

Details Differential gears Differential gears

2002-03-12

2004-06-29

Marmor, Charles A. (Department: 3681)

Planetary gear transmission systems or components

Differential planetary gearing

Bevel gear differential

C475S240000, C475S231000

Reexamination Certificate

active

06755764

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to differential gears having a differential motion limiting function.
2. Description of the Related Art
Among automobile differential gears, those (called limited slip differentials) having a differential motion limiting function, and fashioned so that, when the wheel on one side only tries to freewheel, adequate turning force is still transmitted to the wheel on the other side through clutch means, are widely employed in order to prevent the loss of adequate turning force to the wheel on one side when the wheel on the other side freewheels because it is on ice, snow, or mud or the like, and to prevent the auto-body fishtailing phenomenon when executing a turn or quick getaway or the like.
The differential gears
100
diagrammed in
FIG. 14
, for example, are described in Japanese Patent Publication No. S55-27980/1980 (published) and in Japanese Patent Application Laid-Open No. S58-221046/1983 (published). These differential gears
100
comprise a pair of pressure rings
103
deployed inside a differential case
101
so as to freely move in the direction of wheel axles
102
but be incapable of relative turning, a pinion shaft
104
deployed perpendicularly to the wheel axles
102
in a condition wherein the shaft end is held between the pressure rings
103
, a pinion gear
105
deployed so as to freely turn on the pinion shaft
104
, a pair of side gears
106
deployed to the left and right wheel axles
102
, respectively, so as to be incapable of relative turning, which side gears
106
sandwich the pinion gear
105
and mesh with the pinion gear
105
on either side thereof, actuation means
108
that, in response to increases in relative turning torque between the pinion shaft
104
and the differential case
101
during differential motion, activate the pressure rings
103
in a direction such that the clearance
107
between the pressure rings
103
becomes greater, and clutch means
109
deployed on both sides of the pair of pressure rings
103
in the wheel axle direction, which clutch means
109
limit the differential motion of the left and right wheel axles
102
as the clearance
107
actuated by the pressure rings
103
becomes larger.
For the actuation means
108
, various shapes are proposed. In one example thereof which is adopted, a cam unit
110
having a square shape one diagonal whereof is set in the wheel axle direction is formed on one shaft end of the pinion shaft
104
, and a substantially V-shaped cam channel
111
into which the cam unit
110
engages is formed in the pressure rings
103
.
In the differential gears
100
, moreover, when relative turning torque occurs between the pinion shaft
104
and the differential case
101
, the clearance
107
between the pressure rings
103
will widen due to the actuation means
108
, and, thereby, the clutch means
109
will be activated and the differential motion of the left and right wheels will be limited, but the configuration is made so that, in order that the clearance
107
between the two pressure rings
103
will return to a set interval at normal times, elastic members
112
such as plate springs are positioned outside of the two sets of clutch means
109
in the wheel axle direction, so that the pressure rings
103
are urged in a direction such that they approach each other through a plurality of clutch plates
113
of the clutch means
109
.
Now, in differential gears
100
such as this, it is necessary to secure sufficient area in the friction pressing portion of the clutch plates
113
in order that the differential motion of the left and right wheels will be definitely limited by the clutch means
109
in a differential motion limiting condition. However, the size of the differential case
101
is restricted by the positional relationship between the differential gears
100
and various equipment on the automobile side, making it very difficult to establish that size larger than what it is currently. For that reason, it has been virtually impossible to obtain a more adequate differential motion limiting action than what is obtained currently by increasing the number of clutch plates
113
or making their size larger.
In a horizontal engine vehicle, in particular, as compared to an inline engine vehicle, more severe restrictions are imposed by the layout of the engine and the parts peripheral thereto, and the shape and capacity of the differential case are sharply restricted. As in the differential gears
120
diagrammed in
FIG. 15
, for example, it is necessary to diminish the diameter of the left portion of the differential case
121
, making it very difficult to establish satisfactorily large area in the friction pressing portion of the clutch means
122
. In addition, when the urging force of the elastic members
123
is increased in order to increase the friction pressing force, it becomes impossible to obtain a differential motion condition while effecting a slow turn, as described earlier, wherefore it has been impossible to obtain adequate differential motion limiting action.
The applicant, as a result of assiduous investigations into how to adequately secure friction pressure force in clutch plates, discovered that, whereas configuring the clutch means deployed on either side of the two pressure rings in the wheel axle direction in left-right symmetry was established as one design condition in conventional differential gears, the same kind of differential motion limiting action could be obtained even with one member of the clutch means omitted. Thereupon, the applicant proposed differential gears such as the differential gears
120
A diagrammed in
FIG. 16
, wherein clutch means
122
A are only deployed between the left portion of a differential case
121
A having room to spare and the wheel axle
102
on the left side.
However, even in these differential gears
120
A, a problem developed in that, depending on the shape of the differential case
121
A, with a differential case
121
B wherein the right portion is given a large diameter, as indicated by the imaginary lines in
FIG. 16
, for example, a comparatively large portion of wasted material is formed in the right portion of the differential case
121
B. Besides that, moreover, in the differential gears
100
,
120
, and
120
A described in the foregoing, a side wall
103
a
is formed which extends to the vicinity of the sleeves of the side gears
106
in the pressure rings
103
in order to catch substantially the entire side surface of the clutch plates
113
, but the applicant discovered that the number of clutch plates
113
becomes fewer precisely by the measure of the thickness t of the side wall
103
a
, and that there still exists ample leeway for enhancing the friction pressure force of the clutch plates
113
.
In differential gears such as described above, moreover, it is desirable that, fundamentally, a differential motion condition ensue wherewith maneuvering in tight places can be done when making low-speed turns such as when garaging a vehicle or parallel parking, and that, when one wheel is freewheeling, or a quick getaway is being made, or when turning at high speed or under heavy loading, a differential motion limiting condition ensue wherewith stable initial performance is obtained.
With conventional differential gears, however, as seen in the differential gears
100
, for example, given the relationship whereby the left and right pressure rings
103
are urged by elastic members
112
in a direction such that they will approach each other, via the clutch plates
113
, when the urging force is set to be weak, manipulating the clutch means
109
by the actuation means
108
becomes easy, whereupon there are cases where a differential motion limiting condition will ensue even when making a low-speed turn, and the differential motion condition will not stabilize, whereas, when the urging force is made strong, the actuation means
108
reach a condition where differential motion is possible, but, due to the urging force of the elastic memb

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